1. Field of the Invention
The present invention relates to an electronic control apparatus for driving a boat, which exercises control over driving of a boat, in particular, an electronic control apparatus for driving a boat provided with no mechanical cable or another mechanical links.
2. Description of the Related Art
Conventional examples of an electronic control apparatus for driving a boat of the above-mentioned type include an electronic control system for a boat having no mechanical cable or another mechanical links between a steering position and a propulsion system of the boat, in which the boat is provided with the propulsion system and a steering station including a throttle, a shift, and cruise control elements located at some distance from the propulsion system, the throttle, the shift, and the cruise control elements of the steering station generate electrical signals which are transmitted to an electronic control apparatus in the propulsion system, the electronic control apparatus controls fuel injection and ignition of fuel for the propulsion system and also gives signals to a throttle and a transmission in response to an operator's manipulation of the throttle, the shift, or the cruise control elements, and there is no mechanical links or cables between the throttle, the shift, and the cruise control elements and the propulsion system (see, for example, JP 2000-108995 A).
According to the electronic control apparatus of this type, in order to steer the boat to a forward state or a backward state from a neutral state, a throttle driving part relating to an output of the boat and a shift driving part relating to a moving direction such as forward, neutral, or backward, of the boat, are driven independently of each other as independent driving parts, based on a command value transmitted from the steering station.
In a case of executing steering control for a boat, if a larger load is applied to a screw propeller of a propulsion system when the boat is steered from a neutral state to a forward state or a backward state, it takes longer time to switch the shift position from the neutral state to the forward state or the backward state. In a case where a command for driving the throttle driving part in an output increase direction is given to the throttle driving part from the steering station during when the shift position is being switched, the throttle driving part is driven in the output increase direction without waiting the shift position to reach the movement command value (shift switching completion position), which increases a rotational speed of the engine, leading to problems that a greater shock is given when switching the shift, the shift mechanism of the transmission is damaged due to a great force applied to a mechanical mechanism of the shift because the shift is switched from the neutral position to the forward position or the backward position under a state where the rotational speed of the engine is high, or the shift cannot be changed due to an increase of a torque for switching the shift.
The above-mentioned problems are often caused when the steering lever is suddenly moved from the neutral state to the forward state or the backward state.
In order to solve the above-mentioned problems, there may be provided a portion (so-called play portion) between the throttle (output) command value and the shift (movement) command value calculated from the position of the steering lever, the portion not being driven by the throttle (output) command value and by the shift (movement) command value, and the play portion may absorb time necessary for the switching of the shift. In this case, however, the arithmetic resolution powers of both or one of the output command value and the movement command value calculated from the position of the steering lever are increased, leading to a problem that it is impossible to steer the boat in a meticulous manner.